Occupational load as a risk factor for clinically relevant base of thumb osteoarthritis

It is postulated that increased load from pinch and grasp in occupational tasks increases the risk of thumb carpometacarpal (CMC1) osteoarthritis (OA). We sought to characterise the relationship between doctor-diagnosed CMC1 OA and occupation in a large working population.

We performed a matched case-control study using a Swedish healthcare register. We identified residents aged 30-65 years in 2013 with physician-diagnosed CMC1 OA from 1998 to 2013. We matched four controls per person with CMC1 OA by age, sex, education and postcode. Swedish Standard Classification of Occupations was used to assign occupation. Occupation was categorised as light, light-moderate, moderate and heavy labour. We used conditional logistic regression to estimate ORs with 95% CIs.

We identified 3462 patients with CMC1 OA and matched 13 211 controls. The mean age of the CMC1 OA group was 63 (SD 7) years, with 81% women. The ORs for CMC1 OA in men were 1.31 (95% CI 0.96 to 1.79) for light-moderate, 1.76 (95% CI 1.29 to 2.40) for moderate and 2.00 (95% CI 1.59 to 2.51) for heavy compared with light work. Women had ORs for CMC1 OA of 1.46 (95% CI 1.32 to 1.61) for light-moderate, 1.27 (95% CI 1.10 to 1.46) for moderate and 1.31 (95% CI 1.07 to 1.59) for heavy compared with light work.

The association between increased manual load in occupation and risk of CMC1 OA is more pronounced in men than in women, likely due to higher workload in the heavy labour category.